Clutch facing and process of making same



automobile clutches.

Patented Mar. 30, 1926 UNlTED STATES 1,578,929 I PATENT OFFICE,

' SUMNER SIMPSON, OF BRIIDGEPORT, CONNECTICUT, ASSIGNOR TO LTHE RAYBESTOS I COMPANY, OF BRIDGEPORT, CONNECTICUT, A. CORPORATION OF CONNECTICUT.

CLUTCH FACING Ann raoonss or; MAKING SAME.

No Drawing.

5 Connecticut, have invented an Improvement in Clutch Facings andProcesses of Making Same, of which the following is a specification.

This application is a continuation in part 10. of application'Serial Number 221,002, filed March 7 1918. I The invention relates generally to prpcesses of producing clutch facings, with-more particular reference to'the various typesi-of Itis well knowntliat there are two highly important qualities which, on account; of the natu-reof the work they are called upon to perform, should he possessed by clutch facingsin general, first,

2 they should have a uniformly high" coeflicient of friction, and second, they should be exceedingly tough inorder to withstand the excessive wearing strains of use. ticularly in the case of automobile clutches,

the replacing of'the clutch rings is a laborious and expensive operation, and every effort has been made to produce these rings from material having a requ'isitely high and uniform coeflicient of friction and adapted nt'o withstand the strains of use for the longest possible period of time, It will be apparent, moreover, that in addition to the two essential qualities mentioned aboy'e, in view of the heat which is produced by the friction, clutch rings or' facings sould be constructed of material cav pable of being brought to high temperatures without undergoing either physical or chemical change, and on this acount asbestos has been generally employed as the base for clutch-ring material, for asbestos is not only well known to be capable of withstanding.

high temperatures without chemical or physical change, but it, also possesses the 'requisitely high coeflicient of friction, and

good wearing qualities. v In the mining of asbestos, the mine run includes relatively long fibers, known as crude asbestos, the only part of the run that can be used for spinning, and relatively short fibers, knownas fiber-asbestos, which cannot be spun. The crude asbestos is ship to the spinning mill, where it is crushe opened, carded, roved and spun,

Application filed {une 451 921. Serial No. 475,147.

Par-' and the r twisted around a metallic core, usually small-gauge brass or copper wire, This yarn is then woven'intotape of the desired width and thickness, from 'whi'ch rings of the desired inside and outside diam eter are formed. The rings arethen chemi- ,cally treated and baked at the proper temperature to make them coherent, tough, rela tively hard, and possessed of the desired coelficient of friction. .Wi'th respect to this old process, it will be noted, first, that only a certain selective part of the mined asbestos can be employed-that-is to say, the crude or long- I fiber--asbestosand, second, that the spinning of these long fibers into filameritsythe twisting of these filaments around the metallic core to form reinforced metallic yarn, the weaving of this yarn into fabric, the forming of the fabric into rings of the proper dimensions, and the treating and baking of these rings, constitutes an'elaborate, complex'and necessarily expensive process, the product of which, moreover; is not entirely satisfactory. That the product is 'defective is due to two principal causes; first', because in forming, treating and press.- ing rings of woven fabric it-is impossible toproduce rings which will hold correct inside and outside diameters and uniform thickness, and, second, because woven fabric, however treated, is always subject to a tendency to ravel, particularly after having es of producing asbestos-base clutch rings, 4

in which carding, roving, spinning, twisting and weaving of the raw material is entirely dispensed with; furthermore, a process in which the short-fiber asbestos of the mine run may be utilized, and furthermore, a process y which may be produced integral asbestos-base rings of a homogenous character, not only of uniform-dimensions and contour, but of a character to retain the original size, contour, homogeneity and other qualities throughout long-continued use thereof.

'present invention relates to the percentage of binder incorporatedin the finished ring. I have discovered that the precentage of binder very materially affects the ten- One of the characteristic features of; the I I -sible strengthyand Brinnell hardness of the ring and has an important bearing on the commercial value thereof. For example,

the use of from 10% to 20% ishighly de sirable. It is to be understood, however, that some variation from the above percentages may be allowed in certain cases, either somewhat below 10% or somewhat above 20%. I am here now talking aboutthe use of a drying oil, as for example, such well known drying oils as linseed oil.

Among other analogous ways of carrying out my improved process, I may takethe short-fiber asbestos stock from the mines, mix the same by any approvedprocess of saturation with the proper proportion of 'a suitable liquid binder or binding compound, mold thesame under compressionto the desired form and size and then remove, the facings from the molds and thoroughly dry the same either in the air, or by passing them through a suitable oven. In thismanner, notonly' am I en'- abled to utilize what is known as'low-grade asbestos fiber, but to produce clutch'rings which experiments have. demonstrated will wear longer, give much better-results and be .more eflicient every way than the woven endless or olned rings or. facmgs.

Furthermore, by 'molding under compression, a ring or' facmg from a homogeneous mass of plastic material, the process is carried onwithoutthe excessive waste of materialwhichcannotrbe avoided under present methods of forming these rings from woven tape. Furthermore, it will be-apparent that in mixing the materials to produce the has tic mass from'which the rings are mo ded,

-I am enabl'd' to insure saturation of the asbestos fiberwith the binding material'to a much more nearly perfect degree than is possible in the attempted saturation. of rings formed from woven tape. v I have referred to molding as one..metliod of carrying out the invention. Another method consists in forming 'the' fibrous pulp into a sheet on suit-able "sheet forming mechanism, cutting out the :Eacingsof the required shape and size and then saturating themwith the drying oil binder abovereferred to in the percentages given.- -This oil may then be dried, pref; erably by submitting it to a baking opera-; tion such as previously referred to in con nection with the baking of the woven ring.- This baking should be continued until the rings have the required tensile strength and hardnessto serve their purpose.

-I may still further improve the product of my novel process byincorporating inlthe plastlc compound, prior to compression,

ojs.

metal wire,

preferably copper or brass wire which :may

einthe form of rings, or a "woven mesh, orshort lengths of wire may be indiscriminately dispersed throughout the facings the mass. This metallic reinforcement im parts to the finished rings additional strength, rigidity and toughness.

It is desirable when the asbestos fibers are saturated with the binder before form ing the rings that the fibers and the binder be thoroughly commingled or amalgamated through any-preferred manner of agitation in a suitable container for such period of time as may be required to insure complete saturation of the asbestos fibers, and that after molding or sheeting the rings or sheets be thoroughly dried and baked, ordinarily in a'heatedoven.

The proportions of the ingredients to be employed is a matter of individual judg- 'ment. The ultimate object is to produce a solid homogeneous body in which the fiber predominates. Therefore, just enough .of the binding liquid should be employed to s turate the fiber toan extent which insures substantial solidity and homogeneity under compression. Ordinarily, from 10% to 20% of thelbinder referred to is used and I am now referring .to weight of binder as against the weight of dry. ring before saturation. It is to be understood, however, that some modfication of these proportions is permissible, depending on the tensile strength and hardness required and also somewhat on the character of the asbestos fibre used. v

In case loose fibre isto be saturated about eighty to nine-ty parts by weight of fibre are put into a mixer with about ten to twenty parts by weight of the liquid binder. A'thinner, such as benzol or gasoline, may be added if desired and thernixture churned till the binder has covered all the asbestos fibres.

In 'case the asbestos fibre is fprmed .into

sheets and cut into pieces of the required shape by the gravity of the-saturant, its viscosity and the duration of the immersion. For example, I have found that with a'mixture of about two parts of the liquid binder with one of the thinner at atemper'ature from about seventy degrees to about eighty degree'siF. depending upon the thinner used,

from about ten percent to' about twenty per cent of residual saturant is taken up in onev hour. Residual saturant is the quantity of the binding" material which remainsin the ring after curing.

Uniform density is a matter of prime consideration in the production of these rings, for if the density varies the effects of wearing will be unevenly distributed. and thus 'tend to shorten the useful life of the product. By saturating and thoroughly intermingling the fibers prior to compression,

objectionable, but its presence therein has 'been necessitated in the manufacture of Various materials may" be used for a binder, but in certain circumstances I have found vegetable drying oils are particularly suitable, since they readily penetratelthe fibers, and, upon drying, not only efi'ect the desired cohesion of the asbestos particles,

but waterproof and oilproof'the (product.

The present invention eliminates many expensive operations found in prior processes and removes the necess ty for much costly machinery, besides, making it possible' to use low grade asbestos in the place of the long fiber required for weaving.

having thus described my invention, I claim: I

1. The process of-inaking clutch 'facings which consistsin providing an element composed of unwoven asbestos fibers impregnated with a saturant containing a hardeningbinder and "then curing the element until the required strength and hardness has been secured, the amount of satu-rant being from about 10% .to fibre. I '2. .The process of making clutch facings which consists in providing an element composed of'unwoven asbestos fibers impregnated with a saturant containing a drying oil and then curing the element until'the re-- quired strength and hardness has been secured, the amount of 'saturant being from about 10% to'about 20% of the weight of fiber.-

3. A- clu-tch facing comprising an element formed of unwovenasbestos fibers impregnated with a, saturant containing a hardeningbinder and-cured'to give the required strength and hardness, the amount of the saturant being from about 10% to about 20% of the weight of fiber.

about 20% of the weight of A. A clutch facing comprising an eleinent formed of unwoven asbestos fibers impregnated with a satura'nt containing a drying oil and cured to give the required strength and hardness, the amount of the saturant being from about l0% to about 20% of the weight of fiber.

' In testimony whereof I affix my signature SUMNER SIMPSON. 

